According to a market request for energy saving in these days, there are electrical appliances that continuously operate at extremely low power consumption with respect to the rated power consumption. In electrical appliances including converter circuits, there is a demand for efficient power conversion even during continuous operation at low power consumption.
In particular, in a switching converter in which a semiconductor switch is used, in low power consumption of a load (i.e., a low load), compared with high power consumption of the load (i.e., a high load), the ratio of the power loss of the converter to the input power increases and the converter efficiency is deteriorated. Therefore, various proposals have been made to suppress the converter efficiency deterioration during the low load.
For example, there is proposed a technology for performing control for, when a load requests a relatively low power level, detecting the state of the load, disabling one or more switches among two or more switches according to the detected state to thereby reduce the switching loss and, when additional electric power is required, restoring the one or more already-disabled switches to an operation state to satisfy the power request (e.g., Patent Literature 1).